The split front hinge is now an accepted form as a device which is practical for locking the opening of metallic lens frames. The hinge is first riveted to the seamless frame and the frame and hinge together are then sawed through to allow the frame to open with two parts of the hinge, one part attached to one end and the other part attached to the other end. An assembly screw joins the frame and hinge parts back together and the front hinge and screw serve as a further lock and guard against separation. The problem with this unit has been that all of the locking is done in the hinge back and away from the frame itself. Other frames provide a screw or cylinder and screw machined in the aluminum frame at a place adjacent to the hinge. These frames rely solely on one screw to hold them together and this screw being round there is no actual way for them to be kept from rotating out of alignment.